@megalo/entry/lib/parseConfig.js

解析配置在 `main.js` 或者 `App.vue` 中的 [小程序全局配置](https://developers.weixin.qq.com/miniprogram/dev/framework/config.html#%E5%85%A8%E5%B1%80%E9%85%8D%E7%BD%AE)并生成webpack所需要的entry键值对

const JSON5 = require('json5')
const yaml = require('js-yaml')
const toString = Object.prototype.toString

const handlers = {
  json ({ source, filepath } = {}) {
    return JSON5.parse(source)
  },

  yaml ({ source, filepath } = {}) {
    return yaml.safeLoad(source, {
      filename: filepath,
      json: true
    })
  }
}

function parseConfig ({ source, lang, filepath } = {}, callback) {
  const normalizeMap = {
    json: 'json',
    json5: 'json',
    yaml: 'yaml',
    yml: 'yaml'
  }

  const normalizedLang = normalizeMap[lang]

  const handler = handlers[normalizedLang]

  if (!handler) {
    return callback(new Error(
      'Invalid lang for config block: "' + lang + '", ' +
            'consider using "json" or "yaml"'
    ))
  }

  let config

  try {
    config = handler({
      source,
      filepath
    })

    if (toString.call(config) !== '[object Object]') {
      config = {}
    }

    if (typeof callback === 'function') {
      callback(null, config)
    } else {
      return config
    }
  } catch (e) {
    if (typeof callback === 'function') {
      callback(e)
    } else {
      throw e
    }
  }
}

module.exports = parseConfig